THE IONIZED STRUCTURE OF THE LOCAL SPUR

Abstract

The distribution of the H166α radio recombination line emission at the end of the first quadrant is obtained and compared with the distribution of H I and other young objects. The data analyzed lie in the Galactic longitude range between l = 60° and l = 91° and was observed with single dish antenna at 1.4 GHz. The extended low-density warm ionized medium (ELDWIM) is used to trace the Local Spur (LS), which is strongly correlated with neutral hydrogen and low-brightness H II regions. The Galactic distribution of gas in the (X, Y, z) Galactic coordinates yields the location of ionized hydrogen in an arclike structure at an almost constant distance of 8 kpc from the galactic center. The ELDWIM and the low-brightness H II region define the LS; it is located between r 0.5 and 5 kpc from the Sun. We found sources of ionized gas at larger distances; they are probably located in the Perseus arm. The structure of the LS does not seem to join the Perseus arm at farther distances, a fact gleaned from the H I emission. The LS is very thick between 2 and 5 kpc, where the ionized gas spreads from z –150 to +250 pc. The z distribution of the ionized gas appears tilted with respect to the Galactic plane, which starts at 3 kpc from the Sun and runs toward higher galactocentric radii on the Perseus arm.